1. Field of the Invention
This invention relates generally to a safety apparatus to prevent the tampering or inadvertent human error in operating a tank disconnect or a valve under pressure. More particularly, this invention relates to a disconnect and/or valve safety cover operated with a spring extending means which does not retract unless an air flow is flowing through a pneumatic line whereby the disconnects and/or the valves are covered by the safety cover and not operable except under safe operation conditions.
2. Description of the Prior Art
Safety management of processing gases used in the manufacture of semiconductor devices is very important in the integrated circuit (IC) industry. Particularly, a wide variety of toxic, corrosive, or flammable processing gases are used in the integrated circuit fabrication lines. These hazardous gases must be managed in a "fail safe" manner to prevent leakage into uncontrolled areas. Other than the gas pipes used to contain and transmit the gases from the storage tanks, different kinds of disconnects and valves for controlling the flow of gases through these pipe lines are designed and installed with protective features to increase the safety of the gas management programs.
Recently, with the advent of low cost intelligent microprocessors, the operation and control of the valves have been shifting to rely more on electronic sensors and computers. The operation of the entire gas management system may be continuously monitored through a plurality of sensors and controlled by an on-line computer. Safety prevention networks prevent the disconnects and valves from being manually operated unless certain conditions are satisfied. However, for the purposes of maintenance and for a few exceptional operation conditions, disconnects and valves may be provided with a "manual override" option which would allow an operator to bypass the usual protective functions in operating such disconnects and valves. The safety of such gas system could be jeopardized if a manual override is inadvertently set or if someone intentionally overrides the protective measures with an intention to sabotage.
An on-line automatic pressure interlock device is marketed by Persys Technology Ltd., referred to as "TRIDEX on-line auto pressure interlock" which includes an apparatus to prevent inadvertent disconnection of a gas line in a pressurized system, e.g. a cylinder connection in a gas cabinet. The disclosed safety apparatus includes a cap which covers a tank connection such that human errors in disconnecting gas tank connections may be prevented. The cap position is controlled by an interlock controller which uses the pressure transducers to monitor the on-line pressure for controlling the position of the cap. The safety apparatus disclosed by Persys Technology is useful in providing additional protection, however it is not "fail safe". Since the interlock controller relies on the pressure signals from the pressure transducers for controlling the cap position the protection provided by the TRIDEX device may not be available during a power failure or other types of system malfunctions which may render the pressure transducer data to be erroneously measured or received by the interlock controller. The interlock controller itself may fail to properly control the cap. There is still a need to provide a safety apparatus which is fail safe and does not rely on external power source to provide the protection required by a gas management system even in the time of a power failure or system malfunction.